Implement maps for CVC4, now that it supports constant arrays

reactivate tests for CVC4, if available. Remove non-linear testcase that
worked only on z3 (SumAndMax)
Restore FunDef.orig
Reintroduce liftClosures
Make sure Vanuatoo doesn't throw trivial StackOverflows..
Simplify flattened pre/post
Strings support, fix printing of method calls

- Introduce Leon strings (smt-based solvers only)
  Available in leon.lang.string._

- Print method calls properly, specialize binary ops
Complete support for strings in evaluator/simplestValue
Add script for testing solvers
Always include lib
Use imports
Treat <empty> package
Extract string literals in degenerate cases
Getting active functions, visible from main units + main units
List literals
Synthesis framework refactoring
Fix tests with new synthesis refactoring
Single non-main Units get printed
Imports show to fresh Modules during MethodLifting
Imports show to fresh Modules after RestoreMethods
Literal patterns